Protective cover for a convection microwave oven

ABSTRACT

A microwave oven includes a cooking chamber in which either microwave cooking or hot air convection cooking can be performed. A cooling chamber is situated rearwardly of the cooking chamber for housing a motor and cooling fan. A rear cover of the cooling chamber includes air intake and air exhaust holes formed therein for circulating a cooling air flow produced by the fan. The cover includes a vertical central surface in which the air intake holes are formed, as well as additional surfaces extending obliquely forwardly from respective edges of the central surface. The additional surfaces include a top surface, a bottom surface, and right and left side surfaces. Each of those additional surfaces, except for one of the side surfaces, includes air exhaust holes. Each of the air exhaust holes includes a rearward projection extending thereabove to resist the entry of water. Each of the air intake holes includes a projection extending forwardly from an edge thereof and inclined toward a central axis of the air exhaust hole to resist the entry of foreign objects. A rearward protrusion formed on the central surface serves to space the air intake openings from a surface located adjacent to the microwave oven.

BACKGROUND OF THE INVENTION

The present invention relates to a convection microwave oven having acooking function using a forced convection of hot air heated by anelectric heater in addition to a basic cooking function by means of ahigh frequency energy, and more particularly, to a protective coverinstalled on the back side of a microwave oven to protect and cool a fanmotor.

Generally, a microwave oven is a cooking appliance which cooks foods byfrictional heat generated by causing the molecules of the foods beingcooked to move at high speeds by using high frequency energy. Recently,developed is a convection microwave oven having an additional cookingfunction by forced convection of hot air created by an electric heaterand a blower fan.

In such a convection microwave oven, foods such as meat and fish arecooked evenly from surface to interior by the high frequency energy andat the same time, the surface of the foods is browned to a crisp by thehot air, so that the taste and flavor of foods are enhanced. Of course,the convection microwave oven can only use either the high frequencyenergy or the heater at one time.

FIG. 5 illustrates a prior art convection microwave oven disclosed inJapanese Utility Model Publication No. 57-132118. As shown in FIG. 5,the prior art convection microwave oven has an inner case 1a forming acooking chamber 1 and an outer case 6 surrounding the inner case 1a,wherein an electric component compartment (not shown) for mountingvarious electric components is located between the inner and outer cases1a and 6.

At the back of the cooking chamber 1, a duct 7ais provided between aback side plate 4a coupled to the rear portion of the inner case 1a andthe outer case 6 to form a hot air chamber 7 in which a blower fan 8 andan electric heater(not shown) are provided. To an inner wall of the duct7a, a thick insulating material 7bis fixed to prevent heat radiated fromthe heater from transferring backward. Behind the duct 7a, a cooling fan8a coaxially engaged with the blower fan 8 and a motor 8b for operatingthe cooling fan 8a and the blower fan 8, are also installed.

The duct 7a, the cooling fan 8a and the motor 8b are surrounded by aback side plate 6a coupled to the rear portion of the outer case 6. Theback side plate 6a has a plurality of air vents 9a and 9b for ventingair in accordance with operation of the cooling fan 8a.

In such a prior art convection microwave oven, since the plurality ofair vents 9b, formed in the back side plate 6a of the outer case 6surrounding the motor 8b, are made to pass through from the surface ofthe back side plate 6a, water permeating through these air vents 9bcauses electric leakage or electric breakdown of the motor 8b. That is,if water is dropped on the back side plate 6a of the outer case 6 due tocareless usage, the water does not gravitate to the bottom of the backside plate 6a fall off, but flows inside through the air vents 9b,thereby causing a dangerous short-circuit or breakdown. In addition, dueto the air vents 9b whereby foreign materials can permeate the back sideplate 6a easily whereby, the motor 8b and cooling fan 8a are apt tobecome damaged.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide aprotective cover for a convection microwave oven capable of preventingwater falling along the back side of an outer case from permeatingthrough air vents, and of preventing foreign materials from being ableto penetrate inside.

In order to achieve this object, this invention provides a protectivecover for covering a duct located in back of a cooking chamber, theprotective cover comprising a central surface, a top surface extendedaslant from the central surface, a right side surface extended aslantfrom the central surface, a left side surface extended aslant from thecentral surface, and a bottom surface extended aslant from the centralsurface. The central surface has a plurality of air intake holes forenabling the outside air to be drawn in by a cooling fan coupled to anouter wall of the duct. The top surface, bottom surface, and left sidesurface have a plurality of exhaust holes, respectively, for exhaustingthe air circulated by the cooling fan from inside to outside.

A plurality of rearward guide projections are formed over respectiveexhaust holes disposed on the top surface to prevent water frompermeating to the inside.

Further, a plurality of inward guide projections are extended downwardlyaslant in each of the intake holes formed in the central surface toprevent foreign materials from penetrating to the inside.

In addition, a spacer is projected rearward from the central surface sothat the intake holes are spaced, at a predetermined interval, from anexternal wall.

As mentioned above, since the top portions of the exhaust holes formedon the protective cover are surrounded by the outward guide projections,water does not permeate directly inside the microwave oven through theexhaust holes. Rather, the water bypasses along the outer surface of theprotective cover and then drops down.

Since the intake holes formed on the central surface of the protectivecover have the inward guide projections extended downwardly aslant, eachentrance of the intake holes is not opened to the outside directly, sothat any foreign materials, such as a stick or a pin, can not bepenetrated into the inside through the intake holes carelessly orintentionally.

Further, the intake and exhaust holes are spaced, by a predeterminedinterval, from an external wall by the spacer projected outward from thecentral surface of the protective cover, so that it guarantees freeventilation of the outside air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a convection microwave oven towhich the present invention is applied;

FIG. 2 is a cross-sectional view taken along line 2--2 in FIG. 1;

FIG. 3 is a back side view of a protective cover according to thepresent invention;

FIG. 4 is a cross-sectional view taken along line 4--4 in FIG. 3; and

FIG. 5 is a partial side cross-sectional view showing a schematicconstruction of a prior art convection microwave oven.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, a convection microwave oven to which the presentinvention is applied is comprised of an inner case 10, an outer case 20which forms one assembly together with the inner case 10, and variouskinds of electric components mounted between the inner and outer cases10 and 20. In the back of the inner case 10, a duct 50 and a protectivecover 80 are removably installed.

The inner case 10 is comprised of a front plate 11, a rear plate 12, aleft side plate 13, a right side plate 14, and a bottom plate 16 whichform a cooking chamber 100. In the front plate 11, an opening 17, whichfunctions as the inlet of the cooking chamber 100, is formed. The frontplate 11 includes an upper extending plate 11a, a left extending plate11c, and a right extending plate 11d, each being extended in the upperand left and right directions to a predetermined width. The rear plate12 facing the front plate 11 also includes an upper extending plate 12a,a left extending plate 12c, and a right extending plate 12d, each beingalso extended in the upper and left and right directions to apredetermined width.

The outer case 20 includes an top plate 21, a left side plate 23, and aright side plate 24. Edges of each plate forming the outer case 20 arecoupled to edges of the extending plates forming the front and rearplates 11 and 12 of the inner case 10 to form a main body of themicrowave oven.

Here, lengths from the front to the rear of the plates forming the outercase 20 are equal to the lengths of corresponding plates forming theinner case 10, and the outer case 20 is projected outward from the innercase 10 as far as the widths of the extending plates of the inner case10. The rear plate 12 of the inner case 10 also serves as the rear plateof the outer case 20.

On the front plate 11 of the inner case 10, a door 30 is mounted to openand close the cooking chamber 100, and on the right extending plate 11dof the front plate 11, there is a control panel 40 having a display 41and buttons 42.

In a space formed between the right side plates 14 and 24 of the innerand outer cases 10 and 20, and the right extending plates 11d and 12d ofthe front and rear plates 11 and 12, is provided an electric componentcompartment 200 in which electric components such as a magnetron 201 aremounted.

As shown in FIG. 2, an electric heater 101 functioning as a heatingmeans is installed inside of the cooking chamber 100. The electricheater 101 is pivotally mounted on the upper portion of the cookingchamber 100. A plurality of intake and exhaust holes 121 and 122 forguiding forced convection of hot air are formed in the rear plate 12 ofthe inner case 10, and a duct 50 is arranged at the outside of the rearplate 12. Thus, the intake and exhaust holes 121 and 122 serve tocommunicate the cooking chamber 100 with the duct 50.

In the duct 50, a convecting means 60 and a cooling means 70 areprovided. The convecting means 60 includes a blower fan 61 installedinside of the duct 50, a rotating shaft 62 passing through the duct 50and connected to the blower fan 61, and a motor 63 connected to one endof the rotation shaft 62. The cooling means 70 includes a cooling fan 71coupled to the shaft 62 between the duct 50 and the motor 63.

To protect the duct 50, the cooling fan 71, and the motor 63, aprotective cover 80 having a size large enough to fully cover them isalso mounted on the rear plate 12 of the inner case 10 to define a backwall of a cooling chamber in which the motor 63 and cooling fan 71 aresituated.

FIGS. 3 and 4 show the shape of the protective cover 80 in detail. Asshown in FIG. 3, the protective cover 80 has a central surface as wellas 81, a top surface 82, right and left side surfaces 83 and 84, and abottom surface 85, which are angled obliquely from the central surface81.

A plurality of intake holes 80a are formed on the central surface 81,and a plurality of exhaust holes 80b, 80c, and 80d are formed on the topsurface 82, bottom surface 85, and left side surface 84, respectively(refer to FIG. 3). The right side surface 83 has no exhaust holes. Thereason for this is to prevent the hot exhaust air given off by thecooling fan 71 from being drawn into the electric component compartment200 (refer to FIG. 1) through intake holes 12e, because the intake holes12e are formed on the right extending plate 12d of the inner case 10.

As shown in FIG. 4, on the exhaust holes 80b are formed guideprojections 82a projected outward from the exhaust holes 80b, so that ifwater drips on the exhaust holes 80b, the outward guide projections 82aprevent the water from running into the exhaust holes 80b. The intakeholes 80a formed on the central surface 81 have inward guide projections81a slopped toward the center axis A of the intake holes 80a, so thatforeign materials such as toothpicks or pins can not be inserted intothe intake holes 80a.

Further, a spacer protuberance 81b projected outward from the centralsurface 81 to a predetermined length is formed, so that the intake andexhaust holes 80a and 80b formed on the protective cover 80 are spaced,at a predetermined interval, from an external wall by which themicrowave oven is placed. The outward guide projections 82a, the inwardprojections 81a, and the spacer protuberance 81b are formed integrallywith the protective cover 80.

The operation of the convection microwave oven according to the presentinvention will now be described.

If the start button is depressed to cook the foods by the high frequencyheating, a cooling fan (not shown) located in the electric componentcompartment 200 automatically turns on to draw the outside air in,thereby removing moisture from the inside of the cooking chamber 100.Simultaneously, a high voltage is applied to the magnetron 201, so thathigh frequencies irradiate from the magnetron 201 to the food in thecooking chamber 100 to execute the cooking process.

Also, the food can be cooked by the forced convection of hot airtogether with the high frequency heating as follows.

At first, when the electric power is supplied to the electric heater101, heat is generated by the heater 101. At the same time, by theoperation of the blower fan 61, the air inside the cooking chamber 100is drawn in the area where the blower fan 61 is placed through theintake holes 121 and it is guided upward by the duct 50. The air isagain exhausted to the cooking chamber 100 through the exhaust holes122, so that the heat generated by the electric heater 101 is forced tothe food by the air. Therefore, the heat is dispersed and transferred tothe cooking chamber 100 to cook the food evenly.

With the operation of the electric heater 101 and the blower fan 61, thecooling fan 71 is also operated. When the cooling fan 71 rotates, theoutside air is drawn in the protective cover 80 through the intake holes80a to cool the motor 63, and then it is exhausted through the exhaustholes 80b, 80c, and 80d. At this time, since no holes are formed on theright surface 83 of the protective cover 80, the high temperatureexhaust air can not enter the electric component compartment 200.

As mentioned above, according to the convection microwave oven, becausewater flowing down from the top surface of the protective cover bypassesthe exhaust holes formed on the top surface of the protective cover bythe outward guide projections formed on the exhaust holes, it does notpermeate inside the microwave oven. Rather, the water flows downwardlyand falls off the cover. Therefore, breakdown and short-circuit of themotor installed in the inside of the protective cover can be prevented.

Further, because the intake holes formed in the central surface of theprotective cover have the inward guide projections slanted downwardlytoward the bottom, foreign materials such as small sticks or pins cannot be inserted into the intake holes.

Furthermore, because of the spacer protuberance formed on the centralsurface of the protective cover, the intake and exhaust holes arespaced, at a predetermined interval, from an external wall by which themicrowave oven is placed. Hence the radiation of heat by the cooling fanis achieved effectively.

What is claimed is:
 1. A microwave oven comprising:a housing forming acooking chamber; a high frequency generator for supplying high frequencyto the cooking chamber to perform microwave cooking; a heater forsupplying heat to the cooking chamber to perform convection cooking; acooling chamber disposed rearwardly of the cooking chamber and housing amotor and cooling fan, the cooling chamber including a protective coverdefining a back wall of the cooking chamber; the protective coverincluding a central surface, and a plurality of additional surfaces allextending obliquely forwardly from respective edges of the centralsurface; the additional surfaces including a top surface, a right sidesurface, a left side surface and a bottom surface;the central surfaceincluding air intake holes formed therein, each of the top surface, thebottom surface, and only one of the right and left side surfacesincluding air exhaust holes formed therein.
 2. The microwave ovenaccording to claim 1, wherein the top surface includes projectionsextending rearwardly over respective ones of the air exhaust holesthereof for resisting the passage of water through those air exhaustholes and into the cooling chamber.
 3. The microwave oven according toclaim 2, wherein the central surface extends substantially verticallyand includes projections extending forwardly from an edge of respectiveones of the air intake holes and inclined toward a central axis of therespective holes to resist the entry of foreign objects into the airexhaust holes.
 4. The microwave oven according to claim 3 wherein thecentral surface includes a rearward protuberance extending rearwardlypast the air intake holes to space the air intake holes from an externalsurface located adjacent the microwave oven.
 5. The microwave ovenaccording to claim 1 wherein the central surface extends substantiallyvertically and includes projections extending forwardly from an edge ofrespective ones of the air intake holes and inclined toward a centralaxis of the respective holes to resist the entry of foreign objects intothe air exhaust holes.
 6. The microwave oven according to claim 5wherein the projections are inclined forwardly and downwardly from anupper edge of respective air intake holes.
 7. The microwave ovenaccording to claim 1 wherein the central surface includes a rearwardprotuberance extending rearwardly past the air intake holes to space theair intake holes from an external surface located adjacent the microwaveoven.
 8. The microwave oven according to claim 1, further including acomponents chamber situated next to the cooking chamber for housing thehigh frequency generator; the microwave oven including a rear plate towhich the protective cover is mounted; the rear plate including airintake holes leading to the components chamber, one of the side surfaceshaving no air holes formed therein and situated adjacent the air intakeholes of the components chamber.